Fix handling Inf and Nan values in GiST pairing heap comparator

Previously plain float comparison was used in GiST pairing heap.  Such
comparison doesn't provide proper ordering for value sets containing Inf and Nan
values.  This commit fixes that by usage of float8_cmp_internal().  Note, there
is remaining problem with NULL distances, which are represented as Inf in
pairing heap.  It would be fixes in subsequent commit.

Backpatch to all supported versions.

Reported-by: Andrey Borodin
Discussion: https://postgr.es/m/CAPpHfdsNvNdA0DBS%2BwMpFrgwT6C3-q50sFVGLSiuWnV3FqOJuQ%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Heikki Linnakangas
Backpatch-through: 9.4

diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
index 8360b16ae5016226f19d818b726aa913ebc346a6..154d23400c57133a5de0df8504f42282f0a50b2b 100644 (file)
--- a/src/backend/access/gist/gistscan.c
+++ b/src/backend/access/gist/gistscan.c
@@ -17,6 +17,7 @@
 #include "access/gist_private.h"
 #include "access/gistscan.h"
 #include "access/relscan.h"
+#include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 
@@ -36,8 +37,10 @@ GISTSearchTreeItemComparator(const RBNode *a, const RBNode *b, void *arg)
        /* Order according to distance comparison */
        for (i = 0; i < scan->numberOfOrderBys; i++)
        {
-               if (sa->distances[i] != sb->distances[i])
-                       return (sa->distances[i] > sb->distances[i]) ? 1 : -1;
+               int                     cmp = float8_cmp_internal(sa->distances[i], sb->distances[i]);
+
+               if (cmp != 0)
+                       return cmp;
        }
 
        return 0;